Versatile systems for continuous in-line blending of butane and petroleum

ABSTRACT

A system and method are provided for in-line processes of blending butane into gasoline streams, and for blending butane into a gasoline stream at any point along a petroleum pipeline. The invention additionally provides a method for measuring the vapor pressure and vapor to liquid ratio of the gasoline, both upstream and downstream of the blending operation, as well as the sulfur content of the butane entering the blending operation. The blending operation can be controlled to ensure that the blended gasoline meets EPA requirements for vapor pressure and sulfur content of gasoline. The invention further provides a method for accessing and monitoring the operation off-site.

RELATED APPLICATIONS

This is a continuation of U.S. Ser. No. 13/451,715, filed Apr. 20, 2012,which is a continuation of U.S. Ser. No. 12/633,431, filed Dec. 8, 2009(now U.S. Pat. No. 8,176,951), which is a continuation of U.S. Ser. No.11/407,523 filed Apr. 20, 2006 (now U.S. Pat. No. 7,631,671), which is acontinuation-in-part of U.S. Ser. No. 10/759,515 filed Jan. 16, 2004(now U.S. Pat. No. 7,032,629), which is a continuation of Ser. No.10/071,191 filed Feb. 8, 2002 (now U.S. Pat. No. 6,679,302), whichclaims priority to U.S. Provisional Application 60/267,844, filed Feb.9, 2001. The content of these applications is incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to in-line processes for blending butaneinto a gasoline stream, that allow butane to be blended into a gasolinestream at any point along a petroleum pipeline.

BACKGROUND OF THE INVENTION

Petroleum pipelines are the backbone of this nation's gasolinedistribution system, delivering refined fuel products from ports andrefineries to storage facilities around the country. Through anintricate network of coordinated deliveries from multiple sources,batches of varying grades and types of fuel travel through thesepipelines to predetermined locations. Tank farms are used to store fueldelivered through these pipelines, and to distribute the fuel to othertank farms and ultimately to tanker trucks that deliver the fuel to enduse outlets such as retail gasoline stations. Tank farms that simplystore the gasoline for further distribution to other tank farms arereferred to herein as “intermediate tank farms.” Tank farms thatdispense the gasoline to tanker trucks for delivery to the end user arereferred to herein as “terminal tank farms.” Petroleum products aretypically dispensed to tanker trucks in what is known as a rack, whichusually comprise several outlet ports to which different gasolinetransports may be coupled. Some tank farms are used for terminal andintermediate functions, and those farms are referred to herein as“combined use tank farms.”

A significant physical property of gasoline is its volatility, or itsability to combust. In order to keep cars performing at a consistentlevel year-round, gasoline marketers blend agents such as butane withgasoline to increase the Reid vapor pressure and volatility of thegasoline, especially during the colder months. These marketers also addbutane to reduce the cost of the gasoline. This blending can occurin-line, so that butane is added directly to a line that is transportingthe gasoline. Alternatively, blending can occur in batches, as whenbutane is added to a storage tank.

Because gasoline vapor emissions from automobiles are a major componentof volatile organic compounds (VOC's) in the atmosphere, the UnitedStates Environmental Protection Agency (EPA) has promulgated regulationsthat govern the volatility of gasoline and how much butane can beblended with gasoline. These regulations generally apply from May 1through September 15, when the gasoline is warmest and most volatile,and require that any blended gasoline be certified for compliance withthe volatility guidelines. See 40 C.F.R. §80.27 (2005). The regulationsalso establish maximum volatility levels for gasoline based on theseason of the year, and the region in which the gasoline will bedispensed and sold.

There are two principal methods for assessing the volatility ofgasoline: (1) measuring the vapor to liquid ratio, and (2) measuring thevapor pressure. The Reid method is the standard test for measuring thevapor pressure of petroleum products. Reid vapor pressure (RVP) isrelated to true vapor pressure, but is a more accurate assessment forpetroleum products because it considers sample vaporization as well asthe presence of water vapor and air in the measuring chamber.

The EPA is also concerned with the sulfur contained in butane, and itsemission into the atmosphere when blended gasoline is combusted, and haspromulgated regulations that specify how much sulfur is allowed inbutane that is added to gasoline, and the testing requirements forassuring that the amounts of sulfur do not exceed the specified amounts.See 40 C.F.R. §§80.195, 80.340(a)(1) (2005). The sulfur content of thebutane cannot exceed 30 ppm, and the butane must be sampled at leastonce every 500,000 gallons of butane to assure compliance. See 40 C.F.R.§80.340(a)(1)-(2) (2005).

Butane is often blended with other gasoline components at the refinery,where it is typically added at the trunk line in response to changes invapor pressure demand. An exemplary refinery blending process isdisclosed in Mayer, U.S. Pat. No. 3,751,644. This patent, which is ownedby Sun Oil Company, describes a system for automatically adjusting theamount of butane added to a gasoline stream at a petroleum refinery,based on continuous measurements of the Reid vapor pressure of thegasoline downstream from the point of blending. The described processcalculates the amount of butane to be blended based on measurementstaken downstream of the blending operation, and does not includemeasuring the Reid vapor pressure upstream of the blending operation, orcalculating the blend ratio based on the Reid vapor pressure upstreamfrom the blending operation.

Bajek's U.S. Pat. No. 3,999,959, which is owned by Universal OilProducts Company, also discloses a system for blending butane andgasoline at a petroleum refinery. The Bajek system blends butane with alow-octane gasoline stream and a high-octane gasoline stream, and thenanalyzes the blended gasoline to measure characteristics such as Reidvapor pressure and vapor to liquid ratio. Bajek does not disclosemonitoring the gasoline upstream of the blending operation, orcalculating the blend ratio based upon such upstream monitoring.

Efforts at blending butane at a terminal tank farm have also recentlybeen undertaken. As described in our granted U.S. Pat. No. 6,679,302 (towhich this application claims priority), butane can be blended in-linewith a gasoline stream immediately before the gasoline is dispensed to atanker truck, and after it has been withdrawn from the storage tank. Ina preferred process described in this patent, the Reid vapor pressure ismeasured upstream of the blending operation, and the blend ratio iscalculated based on the upstream measurement.

Lastly, the inventors are aware of an unpatented system that is used toblend butane and gasoline at several terminal tank farms. These systemscontinuously monitor the Reid vapor pressure of gasoline that isintroduced to a storage tank, and blend butane with the gasoline basedupon the vapor pressure measurements. These systems do not continuouslymonitor the Reid vapor pressure downstream of the blending operation asan integrity check. Instead, they certify the integrity of the blendingoperation by periodically measuring the Reid vapor pressure of theentire storage tank.

Several methods have been attempted to improve the precision of butaneblending and the predictability of Reid vapor pressure in the finalproduct. The Grabner unit is a substantial advance in this respect. TheGrabner unit (manufactured by Grabner Instruments) is a measuring devicecapable of providing Reid vapor pressure and vapor to liquid ratio datafor a gasoline sample typically within 6-11 minutes of introducing thesample to the unit. It has been employed at some refineries toconsistently measure the volatility of gasoline, and to blend butanewith the gasoline based upon an allowable Reid vapor pressure for thegasoline.

SUMMARY OF THE INVENTION

By combining the advantages of in-line vapor pressure monitoring bothupstream and downstream of a butane blending operation, the inventorshave developed a tightly controlled butane blending system withsurprising versatility that can be used to blend butane with petroleumproducts at practically any point along a petroleum pipeline, regardlessof variations in the flow rate of gasoline through the pipeline, thetime of year in which the gasoline is delivered, or the ultimatedestination to which the gasoline is delivered. For the first time,petroleum vendors and distributors are able to take optimum advantage ofthe many cost saving and performance benefits that butane blendingoffers, and to do so without regard to the location where the blendingoccurs along the pipeline.

Therefore, in one embodiment the invention provides a system for in-lineblending of gasoline and butane comprising (a) a gasoline stream; (b) abutane stream; (c) a blending unit for blending said gasoline stream andsaid butane stream at an actual blend ratio and an actual blend rate toyield a blended gasoline stream; (d) an upstream vapor pressure sensorin sensory communication with said gasoline stream upstream of saidblending unit; (e) a downstream vapor pressure sensor in sensorycommunication with said gasoline stream downstream of said blendingunit; and (f) one or more information processing units (IPUs) ininformational communication with said upstream vapor pressure sensors,logically programmed to calculate a calculated blend ratio based uponthe vapor pressure of said gasoline stream, and for communicating saidcalculated blend ratio to said blending unit; wherein said blending unitperiodically receives said calculated blend ratio from said IPU, andadjusts the actual blend ratio to coincide with said calculated blendratio.

In one embodiment the gasoline flow rate does not vary over time, andthe blend rate can be calculated based upon a preset gasoline flow rate.Such preset flow rates may occur, for example, when gasoline is pumpedat a terminal tank farm from a tank to a rack, under the influence ofonly one mechanical pump. However, in a particularly preferredembodiment, which takes fuller advantage of the versatility of thesystems described herein, the gasoline flow rate will vary within abatch, and utilizing the invention will further comprise periodicallydetermining the gasoline flow rate through the pipeline, andperiodically recalculating the butane blend rate based upon the gasolineflow rate and the blend ratio calculated by the IPU. In a particularlypreferred embodiment, the gasoline flow rate and gasoline vapor pressurewill be periodically re-determined at the same frequency, so that theblend ratio and blend rate are both periodically recalculated to accountfor differences within and among batches in gasoline flow rate andgasoline vapor pressure. In certain embodiments, the gasoline flow ratemay be continually or continuously received from the operator of thegasoline pipeline. In another embodiment the invention provides a systemfor in-line blending of gasoline and butane comprising (a) a gasolinestream having a volumetric flow rate that varies over time; (b) a butanestream; (c) a blending unit for blending said gasoline stream and saidbutane stream at an actual blend ratio and an actual blend rate to yielda blended gasoline stream; (d) an upstream vapor pressure sensor insensory communication with said gasoline stream upstream of saidblending unit; and (e) one or more information processing units (IPUs)in informational communication with said upstream vapor pressuresensors, logically programmed to calculate a calculated blend ratio andcalculated blend rate based upon the vapor pressure and volumetric flowrate of said gasoline stream, and for communicating said calculatedblend ratio and calculated blend rate to said blending unit; whereinsaid blending unit periodically receives said calculated blend ratio andcalculated blend rate from said one or more IPUs, and adjusts the actualblend ratio and actual blend rate to coincide with said calculated blendratio and calculated blend rate.

In a preferred embodiment the blend ratio and blend rate calculationsare based upon the time of year in which the blending occurs, thedelivery location for the blended gasoline and/or the type of petroleumflowing through the pipeline, because each of these variables governsthe allowable vapor pressure in the gasoline, or whether butane can beblended with the petroleum at all. In one such embodiment, the blendingoperation further comprises an information processing unit and aninformational database on which is stored multiple allowable vaporpressures associated with date and/or destination information, and theinformation processing unit retrieves or receives the date and/ordestination of the gasoline stream, and the information processing unitcalculates the blend ratio and/or blend rate based upon the allowablevapor pressure for the retrieved date and/or destination of the gasolinestream.

In another such embodiment, the blending operation further comprises aninformation processing unit and an informational database on which isstored a listing of one or more petroleum products for which butaneblending is impermissible, wherein the information processing unitretrieves or receives the type of petroleum flowing through the pipelineand the blend ratio and/or blend rate is calculated based upon the typeof petroleum flowing through the pipeline—the rate or ratio equalingzero when a petroleum product to which butane cannot be added is flowingthrough the pipeline.

In yet another such embodiment, each batch of a petroleum product toflow through the pipeline will have an associated batch code based uponthe destination of the batch and/or the type of petroleum product in thebatch, and the blending operation further comprises an informationprocessing unit and an informational database on which is storedallowable vapor pressures for each batch code, and the informationprocessing unit retrieves or receives the batch code associated with thebatch flowing through the pipeline, and the information processing unitcalculates the blend ratio and/or blend rate based upon the allowablevapor pressure for the retrieved batch code. In exemplary embodiments,the rate or ratio equals zero when a petroleum product, such astransmix, to which butane cannot be added is flowing through thepipeline.

The invention will typically be practiced on one skid or platform, suchas a square or rectangular concrete slab situated in proximity to thepoint at which butane is physically added to the pipeline, and it may bepracticed at any point on a pipeline downstream of a refinery. Forexample, the invention may be practiced at an intermediate, terminal, orcombination tank farm, either before gasoline is introduced to a storagetank, or after it is withdrawn from a tank.

In another embodiment, the inventors have developed a combinationmonitoring system that monitors the sulfur content of butane added to agasoline stream and the vapor pressure of gasoline to which the butaneis added. The monitoring equipment for both operations is preferablylocated in the same area, and in one preferred embodiment the vaporpressure and sulfur monitoring equipment is located on the same platformor skid at the tank farm. The butane may be supplied to the monitoringsystem by one or multiple sources of butane, which are typically storedin butane bullets that are located on the premises of the tank farm. Inthis embodiment the invention provides a system for in-line blending ofgasoline and butane comprising (a) a gasoline stream; (b) a butanestream; (c) a gasoline vapor pressure sensor, in sensory communicationwith said gasoline stream; (d) a butane sampling unit for periodicallyor continuously withdrawing butane from said butane stream; and (e) ablending unit for blending said gasoline stream and said butane streamat a blend ratio into a blended gasoline stream, downstream of saidgasoline vapor pressure sensor and said butane sampling unit; whereinsaid butane sampling unit and said gasoline vapor pressure sensor arelocated on a platform in proximity to said petroleum pipeline. Thebutane measurement is preferably made on a semi-automated basis, so thatat least one sample of butane is measured for sulfur content at leastevery 500,000 gallons of butane added to the pipeline.

The apparatus for controlling the blending of the butane and gasolinetypically includes two valves—a modulating valve that controls the flowof butane toward the pipeline, and an on/off valve between themodulating valve and the gasoline stream. The amount of butane permittedto flow through the modulating valve can be varied to achieve anydesired blend ratio, blend rate, or vapor pressure in the blendedgasoline. In one particular embodiment, the modulating valve is underthe control of a process control unit, which varies the blend ratio toattain a desired vapor pressure in the blended gasoline, based on thevapor pressure of gasoline entering the blending unit, the vaporpressure of butane entering the blending unit, and the desired vaporpressure of the blended gasoline. The blend rate is then calculatedbased upon the blend ratio and the rate of flow in the gasoline stream,and the modulating valve is opened or closed to allow butane addition atthe rate thus calculated.

In one embodiment, the invention provides modalities for remotelycontrolling the butane blending operation, and for turning the blendingoperation on or off in its entirety. This may be accomplished, forexample, by controlling the gasoline on/off valve nearest the pipeline,and may be controlled from two or more remote locations, thus giving thepipeline operator, as well as the contract butane blender, control overthe process. The blending operation may be manually overridden when, forexample, the terminal receives a batch of product with which butaneshould not be blended, such as transmix, or at certain times of the yearwhen mixing is impermissible, or in emergency type situations.

It has also proven advantageous to coordinate the butane blendinginformation gathered through the blending operation with data that isoften gathered and generated separately by the tank farm operator, suchas petroleum batch data and rate of flow. The petroleum batch data isparticularly useful because, by knowing the time at which a batch beganpassing, and stopped passing a blending point, one can calculateprecisely how much butane was blended with any given batch of petroleumflowing through the petroleum pipeline. Therefore, in still anotherembodiment the inventors have developed a method of recording thequantity of butane blended with a batch of petroleum in a continuousin-line butane blending operation comprising (a) providing a gasolinestream; (b) providing a butane stream; (c) recording the start time whena batch of gasoline begins to pass through said in-line butane blendingoperation; (d) recording the end time at which the batch finishespassing through said in-line butane blending operation; (e) recordingthe quantity of butane blended with said gasoline stream between saidstart time and end time; and (f) associating said quantity of butanewith said batch in an informational database.

The information gathering and reporting methods of the systems of thisinvention can also be adapted to retrieve, store and generate reportswith useful information such as (i) the date, (ii) batch informationselected from start and stop time, total volume of gasoline per batch,total volume of butane blended per batch, petroleum type, and petroleumdestination, (iii) average blend ratio, (iv) gasoline flow rate, (v)blend ratio, (vi) blend rate, (vii) vapor pressure of said gasolineupstream of the butane blending, (viii) vapor pressure of said gasolinedownstream of the butane blending, (ix) vapor to liquid ratio of saidgasoline upstream of the butane blending, (x) vapor to liquid ratio ofsaid gasoline downstream of the butane blending, (xii) the amount ofbutane in one or more tanks of butane on the tank farm, (xiii) thecontent of sulfur in one or more samples of said butane, (xiv) thepressure of said butane stream at two points along the butane stream,(xv) the settings for daily calibration of a gasoline vapor pressuresensor, and (xvi) the temperature of any butane storage tanks located atthe tank farm. All of this data is preferably accessible at a remotelocation through a suitably programmed information processing andstorage unit.

In still another embodiment the systems of the present invention areprogrammed to automatically vary the blend ratio or blend rate based onthe EPA's vapor pressure limitations based on the time of year andgeographical region. Therefore, in still another embodiment theinvention provides a system for in-line blending of gasoline and butanecomprising (a) a gasoline stream having a volumetric flow rate; (b) abutane stream; (c) a blending unit for blending said gasoline stream andsaid butane stream at an actual blend ratio and an actual blend rate toyield a blended gasoline stream; (d) an upstream vapor pressure sensorin sensory communication with said gasoline stream upstream of saidblending unit; (e) one or more informational databases on which isstored seasonal data that prescribes (i) allowable vapor pressures ontwo or more prescribed dates or ranges of dates, or (ii) whether butaneblending is allowed on two or more prescribed dates or ranges of dates;and (f) one or more information processing units (IPUs) in informationalcommunication with said upstream vapor pressure sensors and saidinformational databases, logically programmed to retrieve the date andto calculate a calculated blend ratio and calculated blend rate basedupon the stored seasonal data and the vapor pressure and volumetric flowrate of said gasoline stream, and for communicating said calculatedblend ratio and calculated blend rate to said blending unit; whereinsaid blending unit periodically receives said calculated blend ratiofrom said IPU, and adjusts the actual blend ratio to coincide with saidcalculated blend ratio.

These and other objects, features, and advantages of the presentinvention may be more clearly understood and appreciated from a reviewof the following detailed description of the disclosed embodiments andby reference to the appended drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram illustrating the architecture of anexemplary butane blending system.

FIG. 2 is a logic flow diagram illustrating an overview of an exemplarybutane and gasoline blending method.

FIG. 3 is a logic flow diagram illustrating an overview of an analysisof the gasoline or blended gasoline streams.

FIG. 4 is a logic flow diagram illustrating operations of the two valvesthat control the flow of butane and gasoline into the blending unit.

FIG. 5 is a logic flow diagram illustrating an exemplary process fordetermining the blend ratio of butane and gasoline, monitoring theblended gasoline, and adjusting the blend ratio if necessary.

FIG. 6 is a functional block diagram illustrating the architecture andcomponents of an exemplary butane blending system.

DETAILED DESCRIPTION OF THE INVENTION

Methods of Measurement

Throughout this patent application, whenever an analysis of gasoline orbutane is disclosed, the analysis is to be performed in accordance withapplicable EPA regulations and American Society for Testing andMaterials (“ASTM”) methods in force as of the date of this application.Therefore, the following ASTM methods are to be used when applicable:

1. For measuring the Reid vapor pressure of reformulated gasoline, ASTMstandard method D 5191-01, entitled “Standard Test Method for VaporPressure of Petroleum Products (Mini Method)” must be used. Thefollowing correlation must also be used to satisfy EPA regulations:RVP_(EPA)=(0.956*RVP_(ASTM))−2.39 kPa

2. For measuring the sulfur content of butane blended with reformulatedgasoline, ASTM standard method D 3246-96 entitled “Standard Test Methodfor Sulfur in Petroleum Gas by Oxidative Microcoulometry” should beused. When blending with conventional gasoline, EPA regulations permitany ASTM sulfur test method to be used for quality assurance testing, solong as the test results are correlated with method D 3246-96.

Discussion

In a first embodiment, the invention provides a system for in-lineblending of gasoline and butane comprising (a) a gasoline stream; (b) abutane stream; (c) a blending unit for blending said gasoline stream andsaid butane stream at an actual blend ratio and an actual blend rate toyield a blended gasoline stream; (d) an upstream vapor pressure sensorin sensory communication with said gasoline stream upstream of saidblending unit; (e) a downstream vapor pressure sensor in sensorycommunication with said gasoline stream downstream of said blendingunit; and (f) one or more information processing units (IPUs) ininformational communication with said upstream vapor pressure sensors,logically programmed to calculate a calculated blend ratio based uponthe vapor pressure of said gasoline stream, and for communicating saidcalculated blend ratio to said blending unit; wherein said blending unitperiodically receives said calculated blend ratio from said IPU, andadjusts the actual blend ratio to coincide with said calculated blendratio.

In a second embodiment, the invention provides a system for in-lineblending of gasoline and butane comprising (a) a gasoline stream havinga volumetric flow rate that varies over time; (b) a butane stream; (c) ablending unit for blending said gasoline stream and said butane streamat an actual blend ratio and an actual blend rate to yield a blendedgasoline stream; (d) an upstream vapor pressure sensor in sensorycommunication with said gasoline stream upstream of said blending unit;and (e) one or more information processing units (IPUs) in informationalcommunication with said upstream vapor pressure sensors, logicallyprogrammed to calculate a calculated blend ratio and calculated blendrate based upon the vapor pressure and volumetric flow rate of saidgasoline stream, and for communicating said calculated blend ratio andcalculated blend rate to said blending unit; wherein said blending unitperiodically receives said calculated blend ratio and calculated blendrate from said one or more IPUs, and adjusts the actual blend ratio andactual blend rate to coincide with said calculated blend ratio andcalculated blend rate.

In a third embodiment, the invention provides a system for in-lineblending of gasoline and butane comprising (a) a gasoline stream; (b) abutane stream; (c) a gasoline vapor pressure sensor, in sensorycommunication with said gasoline stream; (d) a butane sampling unit forperiodically or continuously withdrawing butane from said butane stream;and (e) a blending unit for blending said gasoline stream and saidbutane stream at a blend ratio into a blended gasoline stream,downstream of said gasoline vapor pressure sensor; wherein said butanesampling unit and said gasoline vapor pressure sensor are located on aplatform in proximity to said petroleum pipeline.

In a fourth embodiment, the invention provides a system for in-lineblending of gasoline and butane comprising (a) a gasoline stream; (b) abutane stream; and (c) a blending unit for blending said gasoline streamand said butane stream at an actual blend ratio and an actual blend rateto yield a blended gasoline stream comprising an on/off valve betweensaid gasoline stream and said butane stream and a modulating valve thatmodulates the rate of flow of said butane stream toward said on/offvalve. This embodiment may further comprise an upstream vapor pressuresensor in sensory communication with said gasoline stream, upstream ofsaid blending unit.

In a fifth embodiment, the invention provides a system for in-lineblending of gasoline and butane comprising (a) a gasoline stream havinga volumetric flow rate; (b) a butane stream; (c) a blending unit forblending said gasoline stream and said butane stream at an actual blendratio and an actual blend rate to yield a blended gasoline stream; (d)an upstream vapor pressure sensor in sensory communication with saidgasoline stream upstream of said blending unit; (e) one or moreinformational databases on which is stored seasonal data that prescribes(i) allowable vapor pressures on two or more prescribed dates or rangesof dates, or (ii) whether butane blending is allowed on two or moreprescribed dates or ranges of dates; and (f) one or more informationprocessing units (IPUs) in informational communication with saidupstream vapor pressure sensors and said informational databases,logically programmed to retrieve the date and to calculate a calculatedblend ratio and calculated blend rate based upon the stored seasonaldata, and the vapor pressure and volumetric flow rate of said gasolinestream, and for communicating said calculated blend ratio and calculatedblend rate to said blending unit; wherein said blending unitperiodically receives said calculated blend ratio from said IPU, andadjusts the actual blend ratio to coincide with said calculated blendratio.

The systems of the foregoing embodiments may further comprise a gasolinevapor pressure sensor in sensory communication with said gasoline streamdownstream of said blending unit, as described as part of the firstembodiment. Such embodiments may further comprise one or moreinformational databases in informational communication with saiddownstream vapor pressure sensor, wherein said one or more informationaldatabases periodically receive and store vapor pressure measurementsfrom said downstream vapor pressure sensor. The foregoing embodimentsmay further include a gasoline vapor to liquid ratio sensor, and/or anautomated sulfur measuring unit in sensory communication with saidbutane stream.

Additionally, the systems of the foregoing embodiments may furthercomprise a butane sampling unit for periodically or continuouslywithdrawing butane from said butane stream, as described as part of thethird embodiment. Said butane sampling units may be under the control ofone or more information processing units, wherein said one or moreinformation processing units may cause said butane sampling unit towithdraw into a reservoir at least one sample of butane from said butanestream at least every 500,000 gallons of butane. Said reservoir may bemanually withdrawn periodically from said butane sampling unit, and anybutane contained in said reservoir may be tested for sulfur content.

The systems of the foregoing embodiments may further comprise (a) abutane storage unit; (b) underground piping for transmitting said butanestream from said butane storage unit to said butane blending unit; (c) afirst butane pressure sensor in sensory communication with said butanestream at or near said butane storage unit; (d) a second butane pressuresensor in sensory communication with said butane stream at or near saidbutane blending unit; and (e) a remote information processing unit ininformational communication with said first and second butane pressuresensors, for remotely monitoring and displaying butane pressuresdetected by said first and second butane pressure sensors. Also, theforegoing embodiments may further comprise (a) a butane storage unit;(b) a temperature gauge for measuring the temperature of butane in saidbutane storage unit; and (c) a remote information processing unit ininformational communication with said temperature gauge, for remotelymonitoring and displaying temperatures detected by said temperaturegauge.

Significantly, the blending unit described in any of the foregoingembodiments may comprise two valves, as described as part of the fourthembodiment. One valve is an on/off valve located between the gasolinestream and the butane stream. This valve can prevent gasoline fromentering the blending unit. The second valve is a modulating valve thatcontrols the flow of butane towards the first valve. The second valvecontrols the rate of flow of butane by modulating both the pressure ofthe butane stream passing through the valve as well as the size of theorifice through which the butane stream flows. The modulating valveand/or the on/off valve may be under the control of a process controlunit, which varies the blend ratio to attain a desired vapor pressure,based on the vapor pressure of gasoline entering the blending unit, thevapor pressure of butane entering the blending unit, and the desiredvapor pressure of the blended gasoline. A butane addition rate may thenbe calculated based upon the blend ratio and the rate of flow in thegasoline stream, and the modulating valve may be opened or closed toallow butane addition at the rate thus calculated. The valves may alsobe under the control of one or more remote information processing units.

Additionally, any of the foregoing embodiments may comprise one or moreinformational databases and an information processing unit (IPU), asdescribed as part of the fifth embodiment, for storing seasonal data, aswell as the date, types of petroleum, vapor pressure of gasoline, anddelivery location of said gasoline stream, and then blending based uponsaid seasonal data, date, types of petroleum, vapor pressure, anddelivery location of said gasoline stream. In such embodiments, theblending operation may further comprise an information processing unitand an informational database on which is stored multiple allowablevapor pressures associated with seasonal data, date, petroleum type,and/or destination information. The information processing unit thenretrieves the corresponding date, petroleum type, and/or destination ofthe gasoline stream, and the information processing unit calculates theblend ratio and/or blend rate based upon the allowable vapor pressurefor the retrieved seasonal data, date, petroleum type and/or destinationfor the gasoline stream. As used throughout the present application, theterm “retrieve” includes both retrieving data and receiving data fromanother source. The blending unit described in any of the foregoingembodiments may further comprise an information processing unit and aninformational database on which is stored a listing of any petroleumproducts for which blending with butane is impermissible. In suchembodiments, the calculated blend rate and/or blend ratio may equal zerowhen a petroleum product to which butane cannot be added is flowingthrough the pipeline.

In any of the foregoing embodiments, each batch of a petroleum productto flow through the pipeline may have an associated batch code basedupon the destination of the batch and/or the type of petroleum productin the batch, and the blending operation may further comprise aninformation processing unit and an informational database on which isstored allowable vapor pressures for each batch code. In suchembodiments, the information processing unit may retrieve or receive thebatch code associated with the batch flowing through the pipeline, andthe information processing unit may calculate the blend ratio and/orblend rate based upon the allowable vapor pressure for the retrievedbatch code. In such embodiments, the calculated blend rate or blendratio may equal zero when a petroleum product, such as transmix, towhich butane cannot be added is flowing through the pipeline.

The gasoline stream of the foregoing embodiments may have a gasolineflow rate that does not vary over time, and therefore, the blend ratecan be calculated based upon a preset gasoline flow rate. As usedthroughout this application, the term “flow rate” refers to a volume ofa fluid that flows past a given point over a given period of time.Alternatively, the gasoline stream may have a gasoline flow rate thatvaries within a batch of gasoline, and therefore, utilization of theinvention will further comprise periodically determining the gasolineflow rate through the pipeline, and periodically recalculating thebutane blend rate based upon the gasoline flow rate and a calculatedblend ratio. Specifically, any of the foregoing embodiments blendinggasoline with constant or variable flow rates may further comprise oneor more informational processing units in informational communicationwith said upstream vapor pressure sensors, logically programmed tocalculate a calculated blend ratio and calculated blend rate based uponthe vapor pressure and volumetric flow rate of said gasoline stream, andfor communicating said calculated blend ratio and calculated blend rateto said blending unit; wherein said blending unit periodically receivessaid calculated blend ratio and calculated blend rate from said one ormore IPUs, and adjusts the actual blend ratio and actual blend rate tocoincide with said calculated blend ratio and calculated blend rate.

The foregoing embodiments of the invention may further include a manualswitch to shut down the system. The manual switch may operate to turnoff an on/off valve that may be located between the gasoline and butanestreams. The embodiments of the invention may also include aninformational database for storing data accessible to an informationprocessing unit with access to an Internet connection.

The blending units described in the foregoing embodiments of theinvention may be placed on a skid or platform. The invention may belocated anywhere downstream of a refinery. The invention may also belocated at a gasoline tank farm, either before the gasoline stream isintroduced to a tank, or after the gasoline stream is withdrawn from thetank. The tank farm may be a terminal gasoline tank farm, anintermediate gasoline tank farm, or a combined use tank farm.

Referring to FIG. 1, this illustrates an overview of a preferred exampleof components of the foregoing embodiments. It shows a gasoline stream110 and a butane stream 115 entering an analyzing and blending unit 120,and a blended gasoline stream 125 exiting the analyzing and blendingunit 120 and entering a second analyzing unit 130. The analyzing andblending unit 120 may comprise a blending unit, a sulfur measuring unitin sensory communication with said butane stream 115 and a gasolinevapor pressure sensor and/or vapor to liquid ratio sensor in sensorycommunication with said gasoline stream 110. The second analyzing unit130 may comprise a vapor pressure sensor and/or vapor to liquid ratiosensor in sensory communication with said blended gasoline stream 125.

In a sixth embodiment, the invention provides a method for in-lineblending of gasoline and butane comprising (a) providing a gasolinestream; (b) providing a butane stream; (c) measuring vapor pressure ofgasoline in said gasoline stream; (d) calculating a blend ratio basedupon said vapor pressure; (e) blending the butane stream and gasolinestream at said blend ratio to provide blended gasoline; and (f)measuring vapor pressure of the blended gasoline stream.

In a seventh embodiment, the invention provides for a method for in-lineblending of gasoline and butane comprising (a) providing a gasolinestream having a volumetric flow rate that varies over time; (b)providing a butane stream; (c) periodically measuring vapor pressure ofgasoline in the gasoline stream; (d) periodically measuring volumetricflow rate of gasoline in the gasoline stream; (e) calculating a blendratio based upon said vapor pressure and said volumetric flow rate; and(f) blending, with a blending unit, the butane stream and the gasolinestream at said blend ratio to provide a blended gasoline stream.

In an eighth embodiment, the invention provides a method for in-lineblending of gasoline and comprising (a) providing a gasoline stream; (b)providing a butane stream; (c) measuring vapor pressure of gasoline inthe gasoline stream; (d) calculating a blend ratio based upon said vaporpressure; (e) periodically or continuously withdrawing butane from saidbutane stream; (f) periodically or continuously measuring sulfur contentof the butane withdrawn from said butane stream; and (g) blending thebutane stream and the gasoline stream at said blend ratio to provide ablended gasoline stream.

In a ninth embodiment, the invention provides a method for in-lineblending of gasoline and butane to provide a blended gasoline streamcomprising (a) providing a gasoline stream; (b) providing a butanestream; (c) controlling a blend ratio of butane from said butane streamand gasoline from said gasoline stream at a blending operation; and (d)controlling whether or not gasoline pressure from said gasoline streamenters the blending operation. This method may further comprisemeasuring vapor pressure of the gasoline stream, measuring sulfurcontent of the butane stream, and/or measuring vapor pressure of theblended gasoline stream.

In a tenth embodiment, the invention provides a method for in-lineblending of gasoline and butane to provide a blended gasoline streamcomprising (a) providing a gasoline stream having a volumetric flowrate; (b) providing a butane stream; (c) measuring vapor pressure ofgasoline in the gasoline stream; (d) storing, in one or moreinformational databases, seasonal data that prescribes (i) allowablevapor pressures on two or more prescribed dates or ranges of dates, or(ii) whether butane blending is allowed on two or more prescribed datesor ranges of dates; (e) calculating a blend ratio based upon currentdate information, said seasonal data, and said vapor pressure; and (f)blending, with a blending unit, the butane stream and the gasolinestream at said blend ratio to provide a blended gasoline stream.

In an eleventh embodiment, the invention provides a method of recordingthe quantity of butane blended with a batch of gasoline in a continuousin-line butane blending operation comprising (a) providing a gasolinestream; (b) providing a butane stream; (c) recording a start time when abatch of gasoline begins to pass through said in-line butane blendingoperation; (d) recording an end time at which the batch finishes passingthrough said in-line butane blending operation; (e) recording thequantity of butane blended with said gasoline stream between said starttime and end time; and (f) associating said quantity of butane with saidbatch in an informational database.

The eleventh embodiment may further comprise measuring vapor pressurefor each batch of blended gasoline. The validation may be done using thechill method. This embodiment may further comprise dividing each batchof blended gasoline into different streams of blended gasoline, andsending each stream to an off-site recipient of blended gasoline.

In an twelfth embodiment, the invention provides a method for off-sitemonitoring and collection of data at a gasoline and butane blendingoperation comprising (a) providing a gasoline stream; (b) providing abutane stream; (c) measuring vapor pressure of gasoline in the gasolinestream; (d) calculating a blend ratio based upon said vapor pressure;(e) blending said butane stream and said gasoline stream at said blendratio to provide a blended gasoline stream; (f) recording values thatrepresent one or more of (i) the date, (ii) batch information selectedfrom start and stop time, total volume of gasoline per batch, totalvolume of butane blended per batch, petroleum type, and petroleumdestination, (iii) average blend ratio, (iv) gasoline flow rate, (v)blend ratio, (vi) blend rate, (vii) vapor pressure of said gasolineupstream of the butane blending, (viii) vapor pressure of said gasolinedownstream of the butane blending, (ix) vapor to liquid ratio of saidgasoline upstream of the butane blending, (x) vapor to liquid ratio ofsaid gasoline downstream of the butane blending, (xii) the amount ofbutane in one or more tanks of butane on the tank farm, (xiii) thecontent of sulfur in one or more samples of said butane, (xiv) thepressure of said butane stream at two points along the butane stream,(xv) the settings for daily calibration of a gasoline vapor pressuresensor, and (xvi) the temperature of any butane storage tanks located atthe tank farm; (g) storing said values in an informational database; and(h) providing remote access to said values to an information processingunit with access to an Internet connection.

The foregoing methods may further comprise measuring vapor pressure ofthe blended gasoline stream, as described as part of the sixthembodiment. Any of the foregoing methods may further comprise measuringgasoline vapor-to-liquid ratio upstream and/or downstream of theblending.

Additionally, any of the foregoing methods may further compriseperiodically or continuously withdrawing butane from said butane streamand periodically or continuously measuring sulfur content of the butanewithdrawn from said butane stream, as described in the eighth embodimentdiscussion. These steps may comprise drawing an initial sample of butanefrom said butane stream, placing the initial sample of butane in areservoir, repeatedly drawing subsequent samples of butane from saidbutane stream and placing them in the reservoir until a pre-determinedamount of butane has been blended with the gasoline stream, manuallywithdrawing the reservoir, and measuring the sulfur content of thebutane in the reservoir. A typical pre-determined amount of butane isabout 500,000 gallons of butane. Measuring sulfur content in the butanestream in any of the foregoing methods may alternatively, oradditionally, comprise connecting an automated sulfur measuring unit tothe butane stream.

Any of the foregoing methods may further comprise determining the blendratio of butane and gasoline that will yield a desired vapor pressure inthe blended gasoline and blending said butane stream and said gasolinestream at said blend ratio. Said blend ratio may be determined from thevapor pressure of the gasoline in the gasoline stream and the vaporpressure of butane in the butane stream. Determining the blend ratio canbe accomplished by setting a desired vapor pressure for the blendedgasoline stream, transmitting the desired vapor pressure for the blendedgasoline and the vapor pressure of the gasoline and butane streams to aninformation processing unit, and calculating a blend ratio based on thethree vapor pressure values. After calculating the blend ratio, theblending process in any of the foregoing methods may further comprisemeasuring the vapor pressure of the blended gasoline, transmitting thevalue for the vapor pressure of the blended gasoline to a logic controlunit, and then, using the logic control unit, adjusting the blend ratioof butane and gasoline to achieve the desired vapor pressure in theblended gasoline.

The illustration in FIG. 5 shows an exemplary process for determiningthe blend ratio of butane and gasoline in any of the foregoing methods.The process comprises selecting a desired vapor pressure for the blendedgasoline 505, transmitting values for the desired vapor pressure, alongwith the vapor pressure of the gasoline and butane being blended, to aninformation processing unit 510, and calculating the blend ratio basedon those values 515. The process shown in FIG. 5 further comprisesblending gasoline and butane at the blend ratio to provide blendedgasoline 520, measuring the vapor pressure of the blended gasoline 525,and adjusting the blend ratio as necessary based on the vapor pressureof the blended gasoline and the desired vapor pressure 530.

The blending procedure utilized in any of the foregoing embodiments mayfurther comprise analyzing additional factors beyond vapor pressure,such as the time of year, delivery location, and type of petroleum. Insuch embodiments, the blending procedure may further comprise measuringvapor pressure of the gasoline stream and blended stream, and comparingsaid vapor pressures to allowable vapor pressures based on the time ofyear, the delivery location for the blended gasoline, and the type ofpetroleum flowing through the pipeline. Such embodiments may furthercomprise utilizing an information processing unit and an informationaldatabase on which is stored multiple allowable vapor pressuresassociated with date, petroleum type, and/or destination information,retrieving the corresponding date, petroleum type, and/or destination ofthe gasoline stream with the information processing unit, andcalculating, with the information processing unit, the blend ratioand/or blend rate based upon the allowable vapor pressure for theretrieved date, petroleum type and/or destination for the gasolinestream. In such embodiments, analyzing delivery location and type ofpetroleum may be accomplished by analyzing a batch code that is basedupon the delivery location and type of petroleum associated with eachbatch of petroleum product to pass through the blending operation. Theblending procedure described in any of the foregoing methods may furthercomprise setting a blend rate and/or blend ratio to zero when apetroleum product to which butane cannot be added is flowing through thepipeline.

The blending procedure utilized in the foregoing methods may furthercomprise analyzing volumetric flow rate of the gasoline in the gasolinestream. In any of the foregoing methods, the gasoline in the gasolinestream may have a constant volumetric flow rate. Alternatively, thegasoline in the gasoline stream may have a volumetric flow rate thatvaries within a batch. Where the volumetric flow rate of gasoline in thegasoline stream varies within a batch, any of the foregoing methods mayfurther comprise periodically determining the volumetric flow rate ofthe gasoline and periodically recalculating the blend rate based uponthe gasoline flow rate and the blend ratio. The gasoline flow rate andgasoline vapor pressure may be periodically re-determined at the samefrequency, so that the blend ratio and blend rate are both periodicallyrecalculated to account for differences within and among batches ingasoline flow rate and gasoline vapor pressure.

The rate at which a fluid flows through a valve is a function of thepressure of the fluid exiting the valve, and the area of the orificethrough which the fluid flows through the valve. Therefore, said butanestream and said gasoline stream may be blended at a blend ratio by stepscomprising modulating pressure of the butane stream, modulating area ofan orifice of a valve through which the butane stream flows toward thegasoline stream, and opening an on/off valve along the gasoline stream.FIG. 4 illustrates an exemplary process for blending butane and gasolineat a given blend ratio. The process comprises modulating the pressure ofthe butane stream entering the blending operation 405, modulating thesize of the orifice through which butane enters the blending operation410, and opening an on/off valve along the gasoline stream 415.

In any of the foregoing methods, the butane stream may be fed by asource of butane that comprises a consolidation of multiple butanebullets. The sulfur content of butane may be measured downstream of saidconsolidation of multiple butane bullets.

In any of the foregoing methods, the gasoline stream may comprise aplurality of incoming batches of gasoline, and the blending may yield aplurality of batches of blended gasoline. When the gasoline streamcomprises a plurality of incoming batches of gasoline, the in-lineblending of gasoline and butane and the monitoring of the vapor pressuremay be performed on each batch of incoming gasoline. When the blendingyields a plurality of blended batches, sulfur content and vapor pressurefor each batch of blended gasoline may be validated. The validation maybe done using chill method techniques. Furthermore, each batch ofblended gasoline may be divided into different streams of blendedgasoline, and each stream may be sent to an off-site recipient ofblended gasoline.

Any of the foregoing methods may further comprise measuring vapor toliquid ratio of the gasoline in the gasoline stream and/or in theblended gasoline stream. Measuring the gasoline stream for vaporpressure and/or vapor to liquid ratio can be accomplished by drawing asample of gasoline from the gasoline stream, measuring the vaporpressure and/or vapor to liquid ratio of the sample of gasoline, andreturning the sample of gasoline to the gasoline stream. The vaporpressure and/or vapor to liquid ratio of the gasoline may be measuredevery seven minutes. Likewise, measuring the blended gasoline stream forvapor pressure and/or vapor to liquid ratio can be accomplished bydrawing a sample of blended gasoline from the blended gasoline stream,measuring the vapor pressure and/or vapor to liquid ratio in the sampleof blended gasoline; and returning the sample of blended gasoline to theblended gasoline stream. The measurements of the vapor pressure and/orvapor to liquid ratio may also be done every seven minutes.

FIG. 3 illustrates an exemplary procedure for measuring the vaporpressure and/or vapor to liquid ratio in the gasoline stream or blendedgasoline stream. The procedure comprises drawing a sample from thegasoline or blended stream 305, measuring the vapor pressure and/orvapor to liquid ratio of the sample 310, and returning the sample to thegasoline or blended stream 315.

Any of the foregoing methods may further comprise manually shutting downthe blending operation in emergencies, during periods of time whenblending is not permitted, or if a batch of transmix enters the blendingoperation. Manually shutting down the blending operation may beaccomplished by controlling the on/off valve near the gasoline stream,and said valve may be controlled from two or more remote locations.

Additionally, any of the foregoing methods may further comprise (a)recording values that represent one or more of: (i) the date, (ii) batchinformation selected from start and stop time, total volume of gasolineper batch, total volume of butane blended per batch, petroleum type, andpetroleum destination, (iii) average blend ratio, (iv) gasoline flowrate, (v) blend ratio, (vi) blend rate, (vii) vapor pressure of saidgasoline upstream of the butane blending, (viii) vapor pressure of saidgasoline downstream of the butane blending, (ix) vapor to liquid ratioof said gasoline upstream of the butane blending, (x) vapor to liquidratio of said gasoline downstream of the butane blending, (xii) theamount of butane in one or more tanks of butane on the tank farm, (xiii)the content of sulfur in one or more samples of said butane, (xiv) thepressure of said butane stream at two points along the butane stream,(xv) the settings for daily calibration of a gasoline vapor pressuresensor, and (xvi) the temperature of any butane storage tanks located atthe tank farm; (b) storing said values in an informational database; and(c) providing remote access to said values to an information processingunit with access to an Internet connection.

Referring to FIG. 2, this flow chart diagram illustrates an exemplaryoverview of the blending process of any of the foregoing methods. Theblending process may comprise providing a gasoline stream 205, providinga butane stream 210, analyzing the gasoline stream 215, analyzing thebutane stream 220, selecting a rate at which to blend the streams 225,blending the streams 230, providing blended gasoline 235, and analyzingthe blended gasoline 240.

In any of the foregoing methods, the gasoline stream may comprisereformulated gasoline. Additionally, in the foregoing methods, the vaporpressure measured may be Reid vapor pressure instead of true vaporpressure.

Furthermore, in any of the foregoing methods, the blending and analyzingof butane and gasoline may be performed on one skid or platform.Additionally, any of the foregoing methods may be practiced anywheredownstream of a refinery, including at a rack with a dispensing unit.The method may also be practiced at a gasoline tank farm, either beforethe gasoline is introduced to a tank, or after the gasoline is withdrawnfrom the tank. The tank farm may be a terminal gasoline tank farm, anintermediate gasoline tank farm, or a combined use tank farm.

FIG. 6 is a schematic diagram illustrating in greater detail theexemplary butane blending system described in FIG. 1. Referring to FIG.6, the butane supply 110 comprises a butane tank 205, an inlet line 210,a vapor outlet line 215 and an outlet line 220. The butane tank 205 isfilled with butane through the inlet line 210. Vapor is released fromthe butane tank 205 through 30 the vapor outlet line 215. The butanesupply 110 may further comprise one or more pressure safety valves 225,a level indicator 230, temperature gauges 235, and pressure gauges 240.

Butane is supplied to the analyzing and blending unit 120 by the outletline 220. The butane supply 110 may further comprise a bypass line 245in fluid connection with the butane tank 205 and the outlet line 220.The bypass line 245 is operable for maintaining constant pressure in theoutlet line 220.

The gasoline supply 115 is stored in one or more gasoline tanks 255 atthe tank farm. Different tanks may contain different grades of gasoline.Gasoline is provided to the analyzing and blending unit 120 through oneor more gasoline lines 260.

When a transport arrives at the tank farm, a transport operator selectsa particular grade of gasoline for the transport load. Selection of agasoline grade initiates the analyzing and blending process. A sample ofbutane is drawn from the outlet line 220 and supplied to the analyzer250 where the vapor pressure of the butane is measured. Similarly, asample of gasoline is drawn from the gasoline line 260 and supplied tothe analyzer 250 where the vapor pressure of the gasoline is measured.In an alternative embodiment of the invention, the vapor-liquid ratio ofthe gasoline may be measured instead of, or in conjunction with thevapor pressure, to assess the volatility of the gasoline. Otherembodiments of the invention may measure other physical characteristicsto determine the volatility of the gasoline. A typical analyzer 250 isthe Minivap Online analyzer manufactured by Grabner Instruments.Generally, one or more pumps 280 draw the butane and gasoline samplesinto the analyzer 250. After the analyzer 250 takes measurements, thesamples are returned to the butane outlet line 220 and the gasoline line260. The flow of the butane and gasoline samples is monitored by flowtransmitters 285. Data from the flow transmitters 285 may becommunicated to a processor 265 via remote logic units 290 to ensurethat there is a sample flow to the analyzer 250.

Once the volatility of the samples is measured, the analyzer 250 sendsmeasurement data for the samples to the processor 265. The processor 265calculates the amount of butane that can be blended with the gasoline sothat the maximum allowable volatility of the gasoline is not exceeded.The processor 265 is coupled to one or more programmable logiccontrollers 270 that control injectors 275. The injectors 275 areconnected to the outlet line 220 and control the flow of butane into thegasoline line 260.

What is claimed is:
 1. A system for blending butane with gasoline in apipe, wherein the gasoline has a vapor pressure, comprising: a) a butanereservoir in fluid connection with said gasoline; b) an injector valvefor discharging butane into said gasoline; c) a vapor pressure analyzerconnected to said pipe, said analyzer configured to determine the vaporpressure of the gasoline and to transmit said vapor pressure to aprocessor; d) a programmable logic controller governing the flow ofbutane through said injector valve; and e) a processor programmed toreceive the vapor pressure from the analyzer, calculate an amount ofbutane to inject into the gasoline based on seasonal and/or regionaldata and a maximum preprogrammed volatility limit, and provide a controlsignal to said programmable logic controller according to said seasonaland/or regional data and maximum preprogrammed volatility limit; whereinthe programmable logic controller is configured to adjust the injectorvalve to govern the flow of butane through said injector valve into saidgasoline based on the signal from the processor.
 2. The system of claim1 wherein said processor receives the vapor pressure from said analyzer.3. The system of claim 1 wherein said processor receives the vaporpressure of a blend of gasoline and butane.
 4. The system of claim 1wherein said processor is accessible at a remote location.
 5. The systemof claim 1 wherein said processor is programmed to provide a stopcontrol signal that directs said flow of butane to stop for an intervalof time, and the programmable logic controller is configured to adjustthe injector valve to stop the flow of butane through said injectorvalve into said gasoline in response to said stop control signal.
 6. Thesystem of claim 1 wherein said injector valve is operated by a solenoid.7. A system for blending butane with gasoline in a pipe to form a blendof butane and gasoline, wherein the gasoline and the blend of gasolineand butane each have a vapor pressure, comprising: a) a butane reservoirin fluid connection with said gasoline; b) an injector valve fordischarging butane into said gasoline; c) a vapor pressure analyzerconnected to said pipe, said analyzer configured to determine the vaporpressure of the blend of gasoline and butane, and to transmit said vaporpressure to a processor; d) a programmable logic controller governingthe flow of butane through said injector valve; and e) a processorprogrammed to receive the vapor pressure from the analyzer, calculate anamount of butane to inject into the gasoline based on a maximumpreprogrammed volatility limit, and provide a control signal to saidprogrammable logic controller according to said maximum preprogrammedvolatility limit; wherein the programmable logic controller isconfigured to adjust the injector valve to govern the flow of butanethrough said injector valve into said gasoline based on the signal fromthe processor.